The present invention relates in general to the treatment and management of process fluids used in Dense Phase CO2 applications. More specifically, the present invention relates to an apparatus and process for treating, blending, delivering and recycling CO2 as well as providing clean inert purging or propellant gas for cleaning and extraction systems utilizing solid, liquid and supercritical phase carbon dioxide.
The CO2 cleaning technology developed by the present inventor, and described in detail under issued and pending patents, requires unique process fluid supply requirements not found in conventional CO2 cleaning technology. For example, the TIG-Snow cleaning process described in U.S. Pat. No. 5,725,154, Jackson, teaches the use of both a gas and liquid to produce a cleaning snow (liquid phase) and a propellant (gas phase). Propellant gases may include nitrogen, carbon dioxide or clean-dry-air, among others, and come from a variety of cylinder sources and pressures. The liquid used in the aforementioned invention is liquid carbon dioxide stored under pressure and come in two forms—300 psi and 0F (Vacuum Dewar) and 832 psi and 70F (High Pressure Cylinder). Depending upon the type of cleaning application, various qualities of process fluids may be required to prevent the transfer of contaminants contained within the supply onto critical surfaces during CO2 spray cleaning operations. Contaminants typically found in CO2 and other gaseous process fluid supplies include trace hydrocarbons, silicones, particles and water vapor. Moreover, liquid and supercritical fluid CO2 systems developed and patented by the present inventor require chemical additive, pressure, temperature and, recovery requirements which are very different from those of solid phase carbon dioxide cleaning systems. Moreover, common to most CO2 cleaning processes, regardless of phase used, is a requirement for ultraclean pure process gas for purging, drying and inerting operations.
The conventional approach to providing pure CO2 process fluids is characterized by patchwork and customization. For example, CO2 cleaning processes can be supplied with pure cylinder gases and liquids. Cylinders containing ultra-pure process fluids are available from most large industrial gas supply companies such as Praxair and BOC. These types of fluid supplies may cost between $1.50 and $15.00 (U.S.) per pound delivered. Moreover, bulk supplies of ultrapure process fluids with thermal catalytic treatment units and pumps may be installed but are expensive and do not communicate with or supply all the necessary process fluids in the proper pressure, state and temperature. The cost to deliver this quality of process fluid supply in bulk form makes the CO2 cleaning process prohibitively expensive—especially without recycling and recovery capability.
For example, one such commercial CO2 purification system is offered by Va-Tran Systems, Chula Vista, Calif., which employs a refrigerant-based vapor condenser system. The system may be coupled with a thermal catalytic treatment unit upstream prior to vapor condenser unit to deliver a purified liquid CO2 product. Problems observed by the present inventor and end-users of this type of purifier when used with aforementioned snow cleaning equipment developed by the present inventor include erratic pressure and temperature regulation of the purified process fluid delivered to the cleaning system. Pressure, temperature and delivery control problems become more severe when using the Va-Tran purifier with low-pressure carbon dioxide supplies such as a bulk 300 psi and 0 F tank. Moreover, the Va-Tran system attempts to resolve only one component of a multicomponent process fluid management problem, namely chemical quality. However, in this regard, the Va-Tran approach is incomplete—lacking chemical treatment technology for water vapor, fine particles and volatile hydrocarbons.
In another example, commercial liquid and supercritical carbon dioxide cleaning systems require larger capacities and qualities which cannot be achieved using a commercial purifier such as that offered by Va-Tran. Features not provided include blending of additives, recycling and recovery of spent process fluids. Commercial suppliers of liquid and carbon dioxide cleaning systems typical integrate a custom carbon dioxide recovery system into the cleaning system. Air Liquide offers the COSOLV™ supercritical fluid delivery platform for these types of applications, but does not provide for recovery and recycling of the spent process fluids.
A lack of communication with CO2 applications equipment is another limiting factor. Supply side parameters such as supply volume, delivery capacity and quality, also requires endusers to resort to patchwork and customization to develop a basic process fluids management system for their particular applications equipment. End-users invariably resort to purchasing and patching together independent supply, purification and delivery systems as well as electronic control means to meet all of their process fluid delivery requirements—capacity, purity, phase conditions and control.
Moreover, conventional CO2 process fluids treatment and recycling designs are not energy efficient and require a large footprint for implementation. Typical CO2 recycling systems utilize separate distillation and recovery tanks with separate heating and cooling devices. Vapor treatment technology such as thermal catalytic units introduce significant amounts of heat into the vapor phase during treatment, which requires additional system cooling following treatment and prior to fluidization.
In summary, commercial systems lack integration and standardization—therefore the various carbon dioxide cleaning technology vendors each develop a specific treatment, delivery and recycling platform for their specific CO2 equipment and/or the industrial gas supply companies deliver expensive ultrapure cylinder gases or even a custom on-site treatment unit without a recovery system. Moreover, none of the aforementioned conventional CO2 treatment systems provide for multimedia treatment, delivery and recycling capability. Still moreover, energy efficiency and space utilization are not optimized in conventional technologies.
As such, there is a present need for an on-site standardized and modular CO2 process fluids management platform which provides CO2 process fluids, at various capacities, purity levels, pressures, temperatures and phases. This is particularly true for technology developed by the present inventor, namely coaxial CO2 spray and centrifugal CO2 cleaning technology. However, as can be seen from the above discussion, these same capabilities are needed for other more conventional CO2 cleaning system designs. Moreover, there is a need for a CO2 process fluids management system that can integrate and communicate with CO2 cleaning and assembly equipment using a standard communication platform. Finally, there is a present need for a fluids management system that can blend additives into CO2 process fluids and recover and recycle spent process fluids following end-use applications and is compact and energy-efficient.